The invention relates to an asphalt paving composition made with ester bottoms. The Environmental Protection Agency provides a discussion of asphalt roads at http://www.epa.gov/ttn/chief/ap42/cho4/final/c4s05.pdf which is incorporated herein by reference.
Ester bottoms are a low value by-product of vegetable oil or animal fat refining to produce methyl ester. There is little known value for ester bottoms and they are currently marketed for animal feed, lubricants, or other industrial uses at a low price point.
Asphalt materials are used in a wide variety of applications including but not limited to paving asphalt and asphalt shingles. Paving asphalt must be sufficiently durable to withstand high and low temperature extremes without undue wear, cracking or melting. Paving asphalt hardens while in service (age hardening). Age hardening is caused by an increase in viscosity of the asphalt mixture and the gradual loss of flexibility. The degree and the rate of the hardening of the paving asphalt composition or cement are factors affecting the durability of an applied surface. It is believed that the reaction of the asphalt composition with atmospheric oxygen is the principle cause of asphalt hardening in pavement. Therefore, the asphalt industry has long sought to reduce age hardening.
Some conventional refined asphalts have been found to be incapable of meeting some requirements for resistance to either low temperature thermal cracking or high temperature rutting resistance in certain climates. Modifiers such as elastomers, plasterers, chemical gellants, and chemical modifiers can be effective in improving either, or sometimes both, low temperature thermal cracking or high temperature rutting resistance. These modifiers have varying levels of effectiveness and cost.
Conventional practice to improve low temperature properties adds softer asphaltic compounds, aromatic oils, or other additives to soften or plasticize the asphalt composition. In order to reach acceptable low temperature properties, excessive amounts of soft asphaltic materials or fluxes may be required.
In addition, aromatic oils used in combination with polymers can improve the rutting resistance of asphalt. However, many times, the level of polymer required to reach the desired level of rutting resistance becomes undesirable as a result of excessive cost, rendering the composition not feasible for use as a paving composition.
Asphalt compositions may be derived, as indicated from any well-known bituminous or asphaltic substance obtained from natural sources or derived from a number of sources such as, shale oil, coal tar, and the like as well as the mixtures of two or more of such materials. As indicated, paving grade asphalt compositions are preferred in the present invention. Such paving asphalt compositions are often referred to as viscosity, penetration graded, or performance graded (PG) asphalts having penetration up to 400 as measured by ASTM method D5.
As a result of the 1987 Intermodal Surface Transportation Efficiency Act (ISTEA), a $150 million research study was commissioned in which $50 million was spent towards asphalt research for improving asphalt pavements. As a product of that research which was concluded in 1992, the Strategic Highway Research Program (SHRP) produced what is now known as the Superpave Performance Graded Binder Specification in which asphaltic binders are graded or characterized according to their relative performance in resistance to rutting, shoving or deformation at high temperatures, fatigue at intermediate temperatures, and thermal cracking resistance at low temperatures. Asphalts which normally would be graded either under the penetration or viscosity specifications are now graded as PG (Performance Graded) binders. As such, their designation will be representative of their resistance at both high and low temperature, indicating their useable temperature range (UTR) as a PG AA-BB where AA=high temperature resistance In degrees Celsius and BB is low temperature cracking resistance m minus degrees Celsius, i.e., PG 64-22 would prevent rutting up to 64° C. (147° F.) and low temperature cracking to a minus 22° C. (−72° F.). Preferred asphalts are the performance graded asphalts such as PG 46-40, PG 46-34, PG 46-28, PG 52-40; PG 52-34; PG 52-28: PG 52-22, PG 58-40, PG 58-34, PG 58-28, PG PG 58-22, PG 64-40, PG 64-34, PG64-28, PG 64-22, PG 70-40, PG 70-34, PG 70-28, PG 70-22, PG 76-40, PG 76-34, PG 76-28, PG 76-22, PG 82-34, PG 82-28, or PG 82-22. The PG in the title referring to Performance Graded, the first numeric designation referring to the binders high temperature rutting or deformation resistance temperature range limit. The last numeric designation references the cracking resistance temperature limit of the binder.
Areas of high loading or slow or standing traffic as well as areas where temperature extremes can be experienced in excess of 86° C. (187° F.) between high and low temperature levels will require the use of modifiers to obtain the increased useful temperature range. As a result, it has been common to start with softer asphalts to reach low temperature properties, while adding modifiers such as polymers to achieve high temperature rutting resistance. The use of aromatic oils also aids low temperature properties. As such, extensive levels of polymer addition is required to regain high temperature properties, especially when using aromatic oils. The use of aromatic oils can solvate the polymer to a higher degree and thus require a higher level of polymer to be used to obtain the desired high temperature rutting resistance.
A common practice of softening asphalts in the industry is to add heavy vacuum gas oil (HVGO) to paving asphalt to reach the desired useable temperature range (UTR). HVGO may be added after refining or, in some applications, it is not refined out of the asphalt materials. HVGO is a valuable commodity currently selling at about $150/ton premium over the price of asphalt, depending on the market. Therefore, adding HVGO to asphalt is an undesirable fix as it increases the cost of paving asphalt.
Notwithstanding the considerable efforts previously expended to provide an improved asphalt paving composition, there remains a continued need to increase the useable temperature range and reduce the cost associated with manufacturing asphalt paving materials. The present invention addresses both of these needs.